The present invention relates to a reactor for epitaxial growth, and more particularly to a reactor for epitaxial growth wherein the arrangement of silicon wafer-locating pockets formed in a susceptor provided therein is improved.
For epitaxial growth conducted for growing a single crystal of a semiconductor material on a semiconductor substrate such as a silicon wafer, various reactors, e.g. vertical type reactor, horizontal type reactor and barrel type reactor, have been suitably used according to the purposes.
FIG. 4 shows a schematic view of a conventional vertical reactor for epitaxial growth. In the center of bell jar 1 which is made of, for example, quartz glass, a gas inlet nozzle 2 is provided in order to introduce a hydrogen gas and a gas for the growth of semiconductor crystal, e.g. dichlorosilane gas, into the bell jar 1. Susceptor 3 is provided so as to rotate around the gas inlet nozzle 1. Silicon wafers 4 to be subjected to epitaxial growth are placed on the susceptor 3 and heated by induction heating with induction coil 5 provided under the susceptor 3. The used gas is discharged through gas discharge ports 6.
Susceptor 3 used in this vertical reactor has for example a structure as shown in FIGS. 5 and 6. In FIG. 5 showing a plan view of the susceptor, numeral 31 is outer pockets and numeral 32 is inner pockets, and they provide guides for placing wafers 4. Through-hole 33 is provided in the cneter of susceptor 3, through which the gas inlet nozzle 2 is inserted. The diameters of the outer and inner pockets vary depending on the size of the wafers used, and are usually about 100 mm for 4 inch wafer and about 125 mm for 5 inch wafer.
In a conventional epitaxial growth reactor of this type, an induction current is passed through susceptor 3 by induction coil 5 provided as an heater under the susceptor 3, whereby wafers 4 placed on susceptor 3 are heated from the underside of susceptor 3. Susceptor 3 has a tendency to be lower in temperature at its peripheral portion than its inner portion for the reasons that the peripheral portion of susceptor 3 is easy to be exposed to the stream of the introduced gas and that in particular the peripheral portion crosses the gas stream since susceptor 3 rotates around gas inlet nozzle 2 and for other reasons. The temperature distribution of susceptor 3 in the radial direction is shown in FIG. 7. In order to prevent the temperature drop owing to heat radiation at the peripheral portion of susceptor 3, the induction coil 5 is arranged in close proximity to the susceptor at the peripheral portion thereof and at a short distance from the susceptor at the inner portion thereof, whereby the peripheral portion is intensely heated. While heating the susceptor in such a manner, the temperature of the susceptor is measured by a thermometer at six positions in the radial direction, whereby it is contemplated to keep the temperature uniform throughout the entire surface of susceptor 3.
However, even if apparently uniform temperature is achieved throughout the entire surface of susceptor 3 by such a temperature control, defective products may still be produced.
It is a primary object of the present invention to provide a vertical reactor for epitaxial growth which can achieve epitaxial growth in high yields without causing lattice defects.
The above and other objects of the present invention will become apparent from the description hereinafter.